Twelve ASA physical status I-II patients undergoing pelvic laparoscopy for infertility were enrolled in a study to quantify the effects of CO2 insufflation and the Trendelenburg position on CO2 elimination and pulmonary gas exchange, and to determine the minute ventilation required to maintain normocapnia during CO2 insufflation. Measurements of O2 uptake (VO2), CO2 elimination (VCO2), minute ventilation (VE), FIO2, and respiratory exchange ratio (RQ) were made during three steady states: control (C) taken after 15 min of normoventilation but before CO2 insufflation, after 15 min (L1) and 30 min (L2) of hyperventilation during CO2 insufflation. The FIO2 was controlled at 0.5 and arterial blood gases were used to calculate the oxygen tension-based indices of pulmonary gas exchange. After 15 min and 30 min of CO2 insufflation, the volume of CO2 absorbed from the peritoneal cavity was estimated at 42.1 +/- 5.1 and 38.6 +/- 6.6 (SEM) ml.min-1 respectively, increasing CO2 elimination through the lungs by about 30%. Hyperventilation of the lungs by a 20-30% increase in minute ventilation maintained normocapnia. Despite the CO2 pneumoperitoneum and Trendelenburg position, there was no impairment of pulmonary oxygen exchange as estimated by (A-alpha)DO2. This study demonstrated that a 30% increase in minute ventilation, achieved by increasing tidal volume to more than 10 ml.kg-1, is sufficient to eliminate the increased CO2 load and maintain normal pulmonary O2 exchange during pelvic laparoscopy.